Back pain (e.g., chronic low back pain) affects approximately 30 million people in the U.S. and is the second leading cause of adult disability, which affects approximately 7 million people. Chronic back pain interferes with function, reducing activities of daily living, such as walking, housework, and personal care, and decreases quality of life. In addition, back pain is expensive to treat and leads to reduced productivity and ˜150 million missed work days/year, resulting in total costs of ˜$100-200 billion/year in the U.S. Further, back pain (e.g., low back pain) has a global prevalence of approximately 12% and is likely to increase substantially in the future as the population ages. Chronic back pain is distinct from acute back pain, commonly nonspecific and challenging to treat. While acute back pain (defined as pain lasting 3-6 weeks) may resolve on its own, pain recurrences are common after the initial episode of acute back pain and ˜20% of people affected by acute back pain will develop chronic back pain. Chronic low back pain (characterized as lumbar pain lasting for ≥12 weeks), for example, is typically associated with greater pain intensity scores and bilateral axial pain (as opposed to unilateral or radiating pain). Although pain may originate from anatomical lesions (e.g., herniated intervertebral discs) or damage to soft tissues (e.g., muscles), chronic back pain is nonspecific (unknown cause of pain) in up to 85% of cases. Further, back pain may persist long after injuries to the back heal, making treatment futile with therapies that focus on the initiating cause or transmission of pain signals (instead of targeting the reversal of central pain sensitization for pain relief).
Present treatments for back pain (e.g., chronic and/or acute back pain) are often ineffective, not well tolerated and/or associated with side effects and complications.
Common analgesic medications (e.g., acetaminophen, NSAIDs, muscle relaxants, tricyclic antidepressants, corticosteroids) provide short-term pain relief and commonly produce undesirable side effects (e.g., sedation, gastrointestinal problems). Although analgesics can provide substantial pain relief in some, a large proportion of patients do not experience sufficient pain relief. Further, long-term use is not recommended, e.g., to prevent opioid dependence.
Injections of steroids or anesthetics or radiofrequency (RF) ablation provide short-term pain relief (on the order of a few months), but require frequent re-treatment sessions and are associated with side effects and complications (e.g., increased pain, lightheadedness, headache, infection, and nausea and vomiting). Intrathecal drug delivery is effective for reducing pain and improving function long-term but requires an invasive procedure and long-term implant and is limited by frequent side effects and technical complications that may require reoperation or removal of the device.
Alternative therapies, such as exercise, yoga, or strength training can be effective, but patients often fail to comply with treatment regimens.
Physical manipulation has a low level of risk and can provide short-term pain relief, but requires frequent treatment sessions. Acupuncture is a minimally-invasive procedure and studies have suggested that acupuncture can provide pain relief and improvements in function, but the effectiveness of acupuncture remains controversial. Surgical procedures for back pain (spinal fusion, disc replacement) are highly invasive and complex, irreversible, carry risks of complications, and seldom reduce pain or improve function. Further, reoperation is frequently required for failed back pain surgeries (up to 32%).
Existing methods of electrical stimulation reduce pain by generating paresthesias (i.e., tingling sensations) overlapping the regions of pain. Pain relief using these existing methods persists only for a short time following treatment, suggesting that chronic pain has not been reversed and/or the sensitization of central pain processing has not been addressed. As a result, only a small percentage of patients using existing methods of electrical stimulation experienced clinically significant reductions in chronic back pain post-treatment. Transcutaneous electrical nerve stimulation (TENS) and spinal cord stimulation (SCS) have been investigated for the treatment of chronic back pain and neither provides a suitable option for reliable, effective relief of some types of chronic back pain.
TENS is a non-invasive method to deliver electrical stimulation through surface electrodes to generate paresthesia coverage of the regions of pain. TENS requires frequent treatment sessions to maintain pain relief, but consistent efficacy in chronic back pain has not been demonstrated. Although TENS can be self-administered at home, TENS systems can be cumbersome and not practical for daily use. Also, TENS can activate cutaneous fibers and cause irritation and discomfort, limiting the maximum tolerable stimulation intensity and treatment duration that can be delivered and reducing the potential efficacy of the treatment. TENS, while non-invasive, lacks evidence of effectiveness for chronic back pain and may produce discomfort from stimulation of cutaneous fibers.
Spinal cord stimulation is a method to deliver electrical stimulation through implanted leads connected to an implanted pulse generator to generate paresthesia coverage of the regions of pain. SCS is invasive, associated with device complications and less effective for non-radicular pain. Spinal cord stimulation requires complex and invasive surgery to implant the leads and pulse generator. Spinal cord stimulation has a moderate rate of complications, including additional pain and hardware complications, and as a result, revision surgery, reprogramming, or removal of the stimulator is often required.
In summary, present treatments for chronic back pain seldom provide adequate long-term relief of pain or improvements in function; carry risks of side effects and complications; and/or are invasive.
There remains room in the art of pain management for alternative systems and methods to be used in the treatment of back pain (e.g., chronic low back pain).